Did you know that plants need iron? It’s true! The most important role iron serves in plants is as a catalyst for chlorophyll formation. No iron, no chlorophyll, and therefore no photosynthesis.
Iron is also involved in respiration and enzyme systems. In legumes, this mineral helps with nitrogen fixation.
One excellent source of iron for plants is water that happens to contain it, as this form of the mineral tends to be very easy to absorb.
If your plants need supplemental iron beyond what your water source can provide, composted nettles or blood meal are additional options.
Some soils are naturally iron-deficient, while others are depleted by repeatedly growing iron-hungry plants such as blueberries, rhododendrons, petunias, and snapdragons. In most, cases, however, iron deficiency is brought on by other problems that interfere with a plant’s ability to take up the mineral from the soil:
- Soil compaction.
- pH of 8.0 or higher.
- Phosphorus toxicity.
- Calcium toxicity.
- Copper deficiency.
- Excessive soil moisture.
- Root disease.
Symptoms of iron deficiency in plants include:
- Stunted growth.
- Loss of pigment between leaf veins, particularly on young leaves.
- Small flowers.
- Failure to produce fruit.
- Centipede infestation on azaleas.
Be aware that iron deficiency is hard to differentiate from other types of nutrient imbalances, so you may want to consider advanced soil testing.
If you do determine that there is an iron deficiency in your plants, before you run for an iron-rich fertilizer, try to determine the root cause of the problem. Reduce plant stress as much as possible, and work to improve the soil structure and drainage. Also be sure to correct any other nutritional imbalances that emerge. Usually only plants with a particular affinity for iron will need any supplementation.
Excess levels of iron in the soil are not very common. However, applying severely contaminated water or too much iron-based fertilizer can cause this problem.
Generally, when symptoms of iron toxicity appear in plants, it is more likely to be the result of low pH or another nutrient imbalance. Potassium or zinc deficiency are particularly likely to cause excessive iron uptake.
Plants that are sensitive to excess iron levels include tomatoes, basil, phlox, and impatiens.
Symptoms of iron toxicity include:
- Bronzing or stippling of leaves.
- Sparse, dark-colored roots.
- Reduced yield.
- Manganese deficiency.
- Plant death.
If you detect symptoms of iron toxicity in your plants, the first thing to do is test the soil pH and bring it back to neutral if necessary. If this does not correct the problem, consider having lab testing done to look for another mineral deficiency and correct as needs be.